feat: new slash commands and bug fixes (#23)

## Summary

- **feat**: Add `/remind` owner-only command — sends a meeting waiting room notification to a specified user in `#general`
- **fix**: Prevent duplicate DM notifications when a message matches both `respondToMention` and `notifyNameMention` patterns
- **feat**: Port `/alt-text` and `/query` commands from Cordelia — owner-only, AI-powered, using Amari's personality
- **feat**: Add `/research` command — owner-only, web-search-backed query returning results as a markdown file attachment
- **fix**: Suppress non-critical RetroAchievements fetch errors (job retries every 10 minutes)

Closes #19, #20, #21, #22
Also resolves #2 (unhandled HTTP rejections from RA API)

Reviewed-on: #23
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

commands.json

@@ -1,4 +1,17 @@
 [
+  {
+    "name": "alt-text",
+    "type": 1,
+    "description": "Generate descriptive alt-text for an image.",
+    "options": [
+      {
+        "name": "image",
+        "description": "The image to generate alt-text for.",
+        "type": 11,
+        "required": true
+      }
+    ]
+  },
   {
     "name": "create-ticket",
     "type": 1,
@@ -61,6 +74,47 @@
       }
     ]
   },
+  {
+    "name": "remind",
+    "type": 1,
+    "description": "Sends a meeting reminder notification to the specified user.",
+    "options": [
+      {
+        "name": "user",
+        "description": "The user to send the meeting reminder to.",
+        "type": 6,
+        "required": true
+      }
+    ]
+  },
+  {
+    "name": "research",
+    "type": 1,
+    "description": "Research a topic using web search.",
+    "options": [
+      {
+        "name": "prompt",
+        "description": "The topic or question to research.",
+        "type": 3,
+        "required": true,
+        "max_length": 2000
+      }
+    ]
+  },
+  {
+    "name": "query",
+    "type": 1,
+    "description": "Ask Amari a question.",
+    "options": [
+      {
+        "name": "prompt",
+        "description": "The question you would like to ask.",
+        "type": 3,
+        "required": true,
+        "max_length": 2000
+      }
+    ]
+  },
   {
     "name": "Forward to Naomi",
     "type": 3